Electrical contact resistance heating and soldering device



Oct. 5, 1943. A. SCHOENWALD ELECTRICAL CONTACT RESISTANCE HEATING ANDSOLDERING DEVICE Filed Jan. 24, 1941 INVENTOR. d A LEM/V051? SW07VWA 0 Arromws'ys Patented Oct. 5, 1943 ELECTRICAL CONTACT RESISTANCE HEAT- INGAND SOLDERING DEVICE Alexander Schoenwald, Auburn, N. Y.

Application January 24, 1941, Serial No. 375,780

2 Claims.

This invention relates to a new method and means for the development andutilization of heat by electricity, particularly applicable to use inconnection with the heating of soldering tools, also parts to besoldered, stoves, and for the heating of various and sundry materials,objects and devices.

This invention utilizes the contact resistance phenomena, i. e., whentwo metals or electric conductors touch one another and electric currentis passed through the joint formed thereby. said joint will show anelectric resistance'which is known as contact resistance.

It is a known fact that such electric contact resistance has a very lowresistance value and, therefore, it has been very difiicult anduneconomical to develop sufllcient heat by such contact resistance forcommercial purposes, because the necessary current intensities must bevery high (approximately many times 10,000 amps.) and for this reasonthe conductors must be very heavy.

The principal object of the invention, therefore, is to provide a methodand means of effectively applying the contact resistance principle forthe development and utilization of heat for commercial purposes.

This invention makes it possible to develop suflicient heat quantitiesfor commercial purposes by electrical contact resistance with such lowcurrent intensities that it is now practical with this invention to heatvarious objects, such as soldering tools, stoves under certaincircumstances, and other devices, with greater efficiency than otherforms of construction heretofore used.

This invention makes it possible to heat by electricity such devices assoldering tools, and the like, through the medium of direct metalliccontact and without applying any intermediate insulating materialbetween the heating elements or contacts and the object to be heated.Since intermediate insulating material iseliminated in the use of thisinvention, the heating elements or contacts may be made comparativelysmall, thereby greatly reducing the area of heat. radiation and as aresult thereof the loss of heat by radiation is considerably reduced.Since the heat is transmitted directly to the object to be heatedthrough direct metallic contact without insulation, only a relativelysmall amount of heat energy is required.

The various electrical devices and appliances commonly used requirecertain materials or elements which my invention eliminates. Forinstance, commonl known constructions employ insulating materialsbetween the heating elements and the object to be heated. Obviously, theefficiency of such constructions is very low due to the fact that theamount of heat energy invested or used is much greater than the amountwhich is actually utilized in order to overcome the resistance of theinsulating material. Another disadvantage of such commonly knownconstructions results from the fact that the heating elements used areusually built up either in the form of a wire or ribbon, either in theform of a spiral or coil, in association with insulating material with aspace between each winding. This spacing enlarges the area of heatradiation, further decreasing efiiciency. All such obstacles areovercome by the use of my invention employing the contact resistanceprinciple.

A further object of my invention resides in providing a method and meanswhich will overcome the many difficulties encountered with knownelectrical heating devices, which is simple and durable in construction,inexpensive to manufacture and very efilcient in use.

With these and numerous other objects in view, my invention consists inthe novel features of construction, combination and arrangement ofparts, as will be hereinafter referred to and more particularly pointedout in the specification and claims.

In the accompanying drawing forming a part of this application,

Figure 1 is a schematic view illustrating the relationship of theessential elements to electrical connections;

Figure 2 is a top plan view showing the application of the invention toa soldering unit;

Figure 3 is a fragmentary longitudinal sectional View on an enlargedscale taken through the forward portion of the soldering unit;

Figure 4 is a transverse sectional view, as seen on the line 4-4 ofFigure 3, looking in the direction of the arrows;

Figure 5 is a side elevational view of a modified form of solderingtool; and

Figure 6 is a schematic view of a modification of the invention, showingthe use of polyphase currents.

Referring to the drawing, in which similar reference charactersdesignate similar p a It s throughout the several views, andparticularly to Figure 1 thereof, the numeral I designates a transformerhaving a primary winding 2 and a secondary winding 3, the primarywinding having conductor wires 4 for connection with a source (notshown) of electrical current. A switch may be provided for controllingthe flow of current through the primary winding or same may bedisconnected from the source of current when necessary.

The upper portion of this Figure 1 illustrates a schematic arrangementof the contact resistance system consisting of three metal parts. Themetal part is represents the element or device to be heated, madepreferably of copper, which has a higher specific heat conductivityquality than the other two metal parts II. These metal parts I!represent contacts and are taperedtoward their free or outer ends, asshown at t8, the extreme free ends thereof being in, direct, contact;with the opposite sides of the metal part It}. The metal parts orcontacts H are respectively connected with the ends of the secondarycoil. 3 as shown and transmit through contact resistance the current tqpart I9.

By this arrangement the highest resistance exists at the points ofcontact between the parts i1 and I9, at which points the main quantityof heat is developed, The parts I! being in direct metallic contact withthe metal part I9 and the metal of said latter part being of lower heatresistance than the parts It, the developed heat at the points ofcontact between said parts I! and i9 flows into the metal of part I9where such heat can be accumulated as needed. The heat thus'accumulated'in the part I9 will not flowback into the metal parts I7,except in very small neg,- ligible amounts, because of the specificresistivity of the metals in the parts. I! and also by reason of thefact that the tapered portions id thereof build up an additionalconsiderable resistance at the points of contact with the part ISagainstsuch owin bac of h at.- This a rang me t operate-s subs ant ik a h at. etifie I th ar n men the e i com natio o ifi r nt kin s, c r stea es ccns of th sistanc f henetal parts FL. the res s a c o the metal part I9and the resistance at the points Or conta t b en; t e said ers I? d 2 Inrd r to est te t e hi h s e icien y in. u liz n e h at whic is d ve o edat he ints at centact, between the parts aforesaid, the sum of theresistances of the metals in parts I! and t9. should not be higher thanseveral percent, possibly not over 5% of the. sum of the resistancevalues at the two points of contact between said parts I! n 9,- Th riora t e e m a a t I1 an mu e d m n ioned sha ed and ormed tha theirtotal added resistance is as low as possible n s i not m n i ned so ma la be Weake their ha i al. an e e tr cal. str n th Ex rience a shown t atthe b st re ul s a b n hen he. con a t meta art 1 s dimensioned that itslength,- is not more thanfive im s the length o th longest diagon l thaa be measured on its'cross-section.

As hereto-fore mentioned, my invention is pari u r y ad pted f r use inconnection with n electric soldering tool, although same may bev equallywell adapted for use in other connections. For purposes of illustration,1' have shown in Fig ures'Z to 4, inclusive, one adaptation of theinvention embodied in a soldering unit.

This improved soldering unit includes in its construction thetransformer I heretofore referred to. The secondary winding of thetransformer is connected with bars 5 of high conductive material. Thesebars project forwardly from the'transformer'l and a block of heatresistinginsulating material I is disposed between the rear portions ofthe bars a short distance in advance of the transformer, said insulatingblock being formed with a threaded bore 8 to receive a pair 5 of screws9 which are passed through openings in in the respective bars andengaged with threads in the bore of the block. These screws firmly mountthe insulating block I between the bars and limit; their movement towardeach other. A clamping bolt I I passes through the opening I2 formed inone bar, with its head bearing against the outer side face of said bar,while the opposite threaded end of the bolt passes through a bushing it:of insulation. This outer end of the bolt carries a winged nut I4 which,when turned home, exerts pull upon the bolt to flex th bars toward oneanother. Openings I5 are formed through the bars adjacent their freefront ends to receive the I6 of contact parts I? formed as heretoforeset forth in connection with th illustration in Figure 1. The outer endsof the contacts II1 are tapered as heretofore described, for bitingengagement with opposite side faces of the soldering tip. I3, which isformed of metal, preferably copper, having a greater heat'conductivitythan the'metal from which the contacts Il: are formed. When the nut Idof the clamping bolt is tightened, obviously the tapered ends of thecontacts U. will be drawn into gripping engagement With the solderingtip it and firmly hold same therehetwee Thi t it h d in this manne may ereadily r mo d an anoth t substituted when it is found necessary ordesirable The so de in t n '9: wi l. be q k yeated when the current i apli d, an in e said ou he ut cii he s Q h so e ng ml is no lon required. said he w ll cool ickly and corrosive midst-ion. to n app e t nvolume of the metal part I9 should notbe more.

han fii r me the um o t evo iunes o a the contact m al Parts 11 tha mabe us d i i that pa ti ular unit.

he mcd fiec form o in to w re the conductor Wire 2.!) of the c bl o corpasses hrou h a hand e .2 f med of insulatin mate ial and has its frontend. fi to a U- h PQd head 2,3 which is formed of conductive materialand. spac d a ms 2 ca rin contacts 225 wh ch. co resp nd w th the onacts H. a e rtend inwardly from the arms. for r nni a501- daring tip.7,6, corresponding to the part It. clamping; bolt 2 ass s. th ou h thearms of t e he d o rote Z3. and has a wing d ut 28 which ars a ainst awas er b shin ZQ-and. when i hten d serves to. l the rms tow rd eac sthe ho din t e contacts. 2 in. inni n a e mentwith the soldering tip 26.A second cable 30 has its conductor wire SI passing through the handle3-2of a clamp 33' and fixedto the clamp. This clamp is of a size to beconveniently handled and has jaws at and as and a shew as whichisthreaded through the jaw at. when this form of soldering tool is inuse a metal plate 37, which is adaptedto have another metal piate andthe screw 33 and the screw tightened until In. i ure 5 here as en stated a ar it has gripping engagement with the plate 31. The plate 38 isthen disposed in overlapping engagement with the plate 31 and thesoldering tip 26 applied to the plate 31 close to the edge of the plate38. As soon as said soldering tip 26 touches the plate 3'! a circuitwill be completed, and this soldering tip will be quickly heated andsolder melted to form a. soldered joint between the plates.

In Figure 6 I have shown a further modified form of the invention in theform of a schematic view illustrating the use of polyphase currents. Inthis form, the numeral 39 designates a metal part having a specific highheat conductivity and it is the part to be heated. The metal parts 40are the tapered contacts, similar to the contacts I! in the form shownin Figure 1, same being tapered and having a lower heat conductivitythan the part 39. These parts 40 are connected to current conductors 4|leading to a source of supply (not shown).

From the foregoing description of the construction of my improvedinvention, the operation thereof and the application of same to use willbe readily understood, and it will be seen that I have provided asimple, comparatively inexpensive and eificient means for carrying outthe objects of the invention.

While I have particularly pointed out the elements best adapted toperform the functions set forth, it is apparent that various changes inform, proportion and in the minor detail of construction may be resortedto, within the scope of the appended claims, without departing from thespirit or sacrificing any of the principles of the invention.

Having thu described the invention, what I claim is:

1. In an electric heating device, a source of energy, a plurality ofelectrical conductors, a plurality or contact metals in circuit withsaid conductors and a metal part to be heated arranged in direct contactwith said contact metals, said metal part being formed of a material ofhigh heat conductivity with relation to the material of which saidcontact metals are formed, the length of each contact metal part beingnot greater than five times the length of the longest diameter measuredcross-sectionally thereon, and ends of the contact metals being taperedto provide their greatest resistance at their points of engagement withthe metal part to be heated.

2. In an electric heating device operating on a contact resistanceprinciple, a source of energy, a plurality of electrical conductors,three or more metal parts, one of said metal parts being formed of amaterial of higher heat conductivity than the other ones of said parts,the metal parts having the lower heat conductivity being connected withsaid electrical conductors and the other metal part of higher heatconductivity being gripped between and in direct contact with the freeends of each of the metal parts of lower heat conductivity, the latterbeing tapered smaller toward their respective free ends to enhance thecontact resistance between the same and the metal part of higher heatconductivity.

ALEXANDER SCHOENWALD.

